The use of water-cooled kilns for the disposal of waste material such as municipal solid wastes or toxic wastes has provided excellent results. In a particular such construction of a combustor, as described in U.S. Pat. No. 3,822,651, water-cooled pipes are used to form a generally cylindrical inner surface for waste combustion, while air for combustion is injected through the cylindrical surface through perforations in webs that secure adjacent pipes together. Such combustors have become known as the Westinghouse-O'Connor combustor, or W-OCC for short. The W-OCC combustor, in the nature of a rotary combustor, is generally illustrated in U.S. Pat. No. 3,822,651, the contents of said patent being incorporated by reference herein, and provides for the water-cooled pipes to be secured together by perforated strips which define a plurality of openings intermediate the pipes so that the inner cylindrical surface is gas porous. Controlled amounts of gas, for burning, are delivered through the porous surface to effect combustion of the material fed therein. In current practice the water-cooled pipes and web joints consist of a fillet weld on the inside and outside surfaces. The wall perforations direct the incoming combustion air from an overfire air windbox to the burning surface of the waste, while underfire air supply is directed into the waste.
Various improvements have been made to the combustor described in U.S. Pat. No. 3,822,651. In U.S. Pat. No. 4,066,024, an imperforate wall is formed with a fluidized bed-type combustor used and a charge of sand used in pyrolysis of waste material. In U.S. Pat. No. 4,226,584, a plurality of projections are provided on the cylindrical surface so as to create a pattern to support burning material slightly spaced from the surface and prevent air flow blockage in the combustor. In U.S. Pat. No. 4,724,778 a system for air control is described which substantially minimizes waste resulting from the supplying of excess air, and permits selective control of underfire air and overfire air, as well as giving zone control of air flow for different stages of burning. In U.S. Pat. No. 4,735,156, the lower end of the pipes are formed so that the generally cylindrical surface becomes a conical surface at the lower end of the combustor and the openings in the strips securing the water-cooled pipes together increase in size at the lower end of the combustor. In U.S. Pat. No. 4,735,157 a plurality of water-cooled baffle pipes and a spherical, associate ring header are provided, with the baffle pipes attached to the interior of the generally cylindrical side wall of the barrel, so as to agitate and transport combustible material from the side wall of the combustion barrel into the flame area. In U.S. Pat. No. 4,782,768, slanted openings are provided in the connecting webs for the water-cooled pipes so as to direct the combustion gas supply into the interior of the combustion barrel at an acute angle to a vector corresponding to the direction of rotation of the combustor.
A particular problem of molten aluminum resulting from combustion of municipal waste is addressed in the improvement described in U.S. Pat. No. 4,726,765, the contents of which are incorporated herein. As described therein, municipal solid waste contains significant amounts of aluminum, from cans and other forms of packaging, with molten aluminum from combustion of waste accumulating in the lower portion of the drum which can spill through the air openings in the drum wall into the air ducts. The '765 improvement provides for shallow walls about the side and upper ends of the holes, the upper end of the walls preferably rounded, so as to prevent molten material, typically aluminum, from flowing or dripping through the holes into the windbox.
While all of these improvements to the W-OCC combustor serve the functions for which they were designed, a factor that still remains is the time consuming task of welding webs to adjacent water-cooled pipes to form the inner cylindrical surface. Such webs are generally flat stock about 2.54 to 3.81 cm (1 to 1.5 inch) wide and 1.27 cm (0.5 inch) thick and the ends must be prepared for welding the same to the pipes having an outer diameter of about 5.08 cm (2 inches). Also, the perforated webs are sometimes subject to excessive wear and do not have as long a service life as would be desirable.
It is an object of the present invention to provide a combustor that has perforated connections between adjacent water-cooled pipes that provide longer service life.
It is another object of the present invention to provide a combustor that directs molten aluminum away from perforations between adjacent water-cooled pipes and avoids the problem of aluminum drippings removal from windboxes.
It is a further object of the present invention to provide a method for improved fabrication and assembly of a combustor, which permits a more simple welding procedure between adjacent water-cooled pipes and connecting members which form the generally cylindrical inner surface of the combustor.